Yokogawa ProSafe-RS Modules - SNB10D-425/CU2N

Technical Dossier

Product Details And Specifications

Yokogawa ProSafe-RS Series Technical Notes

The Evolution of ProSafe-RS Architecture

Yokogawa introduced the ProSafe-RS platform in 2003 as a purpose-built SIS, replacing the relay-based and early programmable safety systems that preceded it. The initial release established the core architectural principle: a physically isolated safety execution environment with a dedicated safety CPU (SCP) communicating over a redundant Vnet/IP safety bus, separate from the process control network.

Generation 1 (R1.xx – R2.xx, 2003–2008): The foundational hardware set introduced the SNB10D safety node unit as the primary I/O chassis, the SCP401 as the single-CPU safety controller, and a range of SIO (Safety I/O) modules covering discrete and analog signal types. Communication with CENTUM CS 3000 was achieved via the SER (Safety Engineering and Runtime) interface. Hardware in this generation is now classified as mature/end-of-life by Yokogawa; original manufacturer support for repair and replacement has been discontinued for most components.

Generation 2 (R3.xx – R4.xx, 2009–2015): This revision introduced the SCP451 dual-CPU redundant safety controller, significantly improving fault tolerance and diagnostic coverage. The SBU (Safety Bus Unit) was introduced to extend the safety bus across larger plant topologies. I/O module density increased, and the platform gained formal TÜV certification for SIL 3 in both hardware fault tolerance configurations. Integration with CENTUM VP became the standard deployment pattern.

Generation 3 (R4.05 onward, 2016–present): Current production hardware. Enhancements include expanded cybersecurity hardening, improved diagnostic self-test intervals, and compatibility with Yokogawa's OpreX Safety architecture. The SCP401 has been superseded by the SCP451 in new installations, though SCP401 remains in service across a large installed base. Backward compatibility between generations is limited: Generation 1 I/O modules are not electrically or firmware-compatible with Generation 3 CPUs without engineering review. This compatibility constraint is the primary driver of demand for original-generation spare parts.

ProSafe-RS Full Catalog & Functionalities (SKU List)

The following catalog covers the primary module types across the ProSafe-RS platform. Modules are grouped by functional category. All SKUs listed are verified part numbers from Yokogawa's published documentation and field-confirmed procurement records.

Safety Node Units (Chassis)

• SNB10D-425/CU2N: Safety Node Unit, 10-slot backplane, 24 VDC power input, dual-bus connection, standard node configuration for ProSafe-RS I/O expansion
• SNB10D-425/CU2: Safety Node Unit, 10-slot backplane, 24 VDC, single Vnet/IP bus connection, used in simplex node configurations
• SNB10D-225/CU2N: Safety Node Unit, 10-slot backplane, 24 VDC, compact variant for space-constrained installations

Safety CPU Controllers (SCP)

• SCP401-10: Safety CPU Module, single processor, SIL 3 rated, executes safety application logic, primary controller for Generation 1 and 2 installations
• SCP401-20: Safety CPU Module, enhanced memory variant of SCP401-10, supports larger safety application programs
• SCP451-10: Dual-redundant Safety CPU Module, SIL 3, hot-standby redundancy, primary controller for Generation 2 and 3 installations
• SCP451-20: Dual-redundant Safety CPU Module, expanded memory, supports complex safety logic with high I/O point counts

Safety Digital Input Modules (SDI)

• SDV144-S00: 16-channel Digital Input Module, 24 VDC, SIL 3, field device status monitoring for discrete safety inputs
• SDV144-S10: 16-channel Digital Input Module, 24 VDC, with enhanced diagnostics and short-circuit detection per channel
• SDV541-S00: 8-channel Digital Input Module, 120 VAC, SIL 3, for legacy field wiring at higher voltage levels

Safety Digital Output Modules (SDO)

• SDV244-S00: 16-channel Digital Output Module, 24 VDC, SIL 3, drives solenoid valves and discrete actuators in safety shutdown circuits
• SDV244-S10: 16-channel Digital Output Module, 24 VDC, with load current monitoring and open-circuit diagnostics

Safety Analog Input Modules (SAI)

• SAI143-S00: 8-channel Analog Input Module, 4–20 mA HART, SIL 3, for pressure transmitters, temperature transmitters, and flow measurement in safety loops
• SAI143-S10: 8-channel Analog Input Module, 4–20 mA HART, with enhanced HART pass-through for field device diagnostics
• SAI543-S00: 4-channel Analog Input Module, high-accuracy variant, used in custody transfer and critical measurement applications

Safety Analog Output Modules (SAO)

• SAO143-S00: 8-channel Analog Output Module, 4–20 mA, SIL 3, drives control valves and positioners in partial stroke test configurations

Safety Bus Units & Communication

• SBU100-10: Safety Bus Unit, extends Vnet/IP safety bus between node cabinets, supports fiber optic and copper interconnect
• SER100-10: Safety Engineering and Runtime Interface, provides communication link between ProSafe-RS and CENTUM VP/CS 3000 for integrated alarm management and data exchange

Sourcing Hard-to-Find & Obsolete ProSafe-RS Parts

Yokogawa has formally discontinued active production and repair support for Generation 1 ProSafe-RS hardware (SCP401 series, early SNB10D variants, SDV144-S00, SAI143-S00 in original revision). For plant operators maintaining these systems, the secondary market is the primary sourcing channel for like-for-like replacement modules.

Modules covered under DriveKNMS lifecycle support include but are not limited to: SCP401-10, SCP401-20, SNB10D-425/CU2N, SNB10D-425/CU2, SDV144-S00, SDV244-S00, SAI143-S00, SAO143-S00, and SBU100-10.

Quality Control for the ProSafe-RS Range

ProSafe-RS modules present specific quality verification challenges due to their safety-rated backplane communication architecture and dual-bus topology. Standard functional testing procedures applied to conventional PLC I/O modules are insufficient for safety-rated hardware.

DriveKNMS applies the following test protocol to all ProSafe-RS modules prior to dispatch:

• Visual and mechanical inspection: Connector pin integrity, backplane edge connector condition, housing integrity, label and revision marking verification
• Power-on self-test (POST) verification: Module is powered in an isolated test rig; internal diagnostic LED sequence is recorded and compared against Yokogawa's published POST pass criteria
• Backplane communication test: Module is inserted into a ProSafe-RS test chassis and polled via the Vnet/IP safety bus to confirm correct node address response and communication integrity
• I/O channel functional test: For digital modules, each channel is exercised with a calibrated signal source and the output state is verified. For analog modules, a 4-point calibration check (0%, 25%, 75%, 100% of range) is performed and results are logged
• HART communication verification (analog modules): HART pass-through is confirmed using a HART communicator connected to each channel
• Firmware revision documentation: Firmware version is read from the module and recorded in the test certificate issued with each unit

All test results are documented in a module-specific test certificate provided with each shipment. Modules that fail any test step are quarantined and not offered for sale.